Hydrocarbon polymers having alicyclic skeletons in their molecules (alicyclic hydrocarbon polymers) have been used as materials for various industrial parts because of their excellent specific inductive capacity, transparency, dimensional stability under heat, solvent resistance and flatness. Such alicyclic hydrocarbon polymers have hitherto been produced by polymerizing or copolymerizing petroleum-derived monomers, or by hydrogenating polymers obtained thereby. For example, patent document 1 (U.S. Pat. No. 6,486,264) proposes a process for producing a hydrogenated ring-opening polymer of a cyclic olefin by conducting ring-opening metathesis polymerization of the cyclic olefin, and then performing hydrogenation. Further, patent document 2 (U.S. Pat. No. 6,365,686: Translation of PCT application) and patent document 3 (U.S. Pat. No. 6,316,560) disclose a cycloolefin copolymer: an alicyclic hydrocarbon polymer, which is obtained by copolymerizing a cyclic olefin and a chain olefin in the presence of a specific catalyst.
Furthermore, the alicyclic hydrocarbon polymers have hitherto been widely used particularly as lenses and various film-shaped or sheet-shaped optical materials because of their amorphousness and high transparency. Specifically, patent document 4 (US 20050151890) shows an optical film composed of a polymer containing an alicyclic structure.
However, although the above-mentioned alicyclic hydrocarbon polymers are small in specific gravity and light in weight as compared to conventional methacrylic resins and carbonate resins, alicyclic hydrocarbon polymers and other polymers lighter in weight have been demanded under the recent circumstances that weight saving has been demanded to various resin formed articles.
On the other hand, for the formation of a recycling-based society, the prevention of global warming and the like, attention has recently been attracted to effective utilization of plant-derived biomass from the viewpoint of carbon neutrality. For example, as one of natural biomass which is abundantly found in the natural world, there are terpenes which are largely contained in pine resin, rind of citrus fruits and the like. Such terpenes have been widely used as raw materials for pharmaceutical compounds and perfumes.
Some terpenes used herein have an alicyclic vinyl monomer structure, and have been known from long ago to have polymerizability. Cationic polymerization of β-pinene which is one of the terpenes is described in non-patent document 1. However, an alicyclic hydrocarbon polymer obtained according to a technique described in non-patent document 1 had a small molecular weight and was insufficient in heat resistance and strength. Accordingly, even the use of such a polymer described in non-patent document 1 could not provide a stable formed article and the like, and it was difficult to use the polymer as a material for the formed article. Therefore, it was only used industrially as a resin additive or a tackifying resin.
Further, non-patent document 2 describes that a polymer having a relatively large molecular weight was obtained by adding 2,6-di-t-butyl-4-methylpyridine in cationic polymerization of β-pinene. However, the glass transition temperature of the polymer obtained therein was 65° C., which was insufficient for practical use.
Patent Document 1: U.S. Pat. No. 6,486,264
Patent Document 2: U.S. Pat. No. 6,365,686
Patent Document 3: U.S. Pat. No. 6,316,560
Patent Document 4: US 20050151890
Non-Patent Document 1: William J. Roberts and Allan R. Day, “A study of the Polymerization of α- and β-Pinene with Friedel-Crafts Type Catalysts”, Journal of the American Chemical Society, vol. 72, pp. 1226-1230 (1950), U.S.A.
Non-Patent Document 2: B. Keszler, J. P. Kennedy, “Synthesis of High Molecular Weight Poly (β-Pinene)”, Advances in Polymer Science, vol. 100, pp. 1-9 (1992), Germany